Prussian blue, discovered in 1704 or 1705, is generally regarded as the first of the modern colors. In truth it is something of an anomaly, appearing well before the blossoming of chemistry as a science in the late eighteenth century. Like so many other innovations in color, it was the result of a serendipitous accident.
|Current Names ||English: Prussian blue |
French: bleu prussien, bleu de Prusse
German: Preussisch Blau
Italian: azzurro di Prussia
Japanese: konjō, berensu
Russian: берлинская лазаурь
Spanish: azul de Prussia
|Synonyms ||English: Berlin blue, iron blue, Milori blue, Paris blue, Turnsbull blue |
German: Berlinerblau, Pariserblau, Turnbullsblau
Italian: azzurro di Berlin
Spanish: azul de Berlin
Origin and History
A Berlin-based color maker, Heinrich Diesbach, was working in the laboratory of the alchemist Johann Konrad Dippel, and in the course of preparing a red lake pigment, Diesbach asked Dippel for some potash (a potassium alkali).
Presumably to economize, Diesbach requested a batch of potash contaminated with oils prepared from animal blood. It was a false economy, for his pigment turned out very pale. Attempting to concentrate it, he succeeded instead in turning it deep blue. He had no idea what had transpired, but was astute enough to recognize the blue material as a potential pigment in its own right, and was soon manufacturing it according to a jealously guarded recipe.
Iron blue was first mentioned in 1710 in a Latin text written by an unknown author and its properties were described in a reference from 1726. It is said to have been discovered by the chemist and painter Diesbach in 1704, but other sources mention the chemist Johann Conrad Dippel, for whom Diesbach worked.
The first mention of its manufacture was by the English chemist John Woodward in 1726. Potash and ox blood were heated until they glowed and then subsequently boiled with rainwater. The "blood lye" obtained in this way was heated together with a sulfate and alum. This produced a green intermediate product, also called "mountain green" or "crysocollage green." The material was then washed and filtered. After a treatment with hydrochloric acid, the product eventually turned to a deep blue color. It was particularly valued for mixing light blues, and appears in skies by Watteau, Canaletto and Gainsborough.
Our Prussian blue is made according to the process originated by the French colormarker, Milori & Company, Lyons, France, known as the Milori process.
Permanence and Compatibility
Prussian blue is stable in weak acids, but is decomposed by weak alkalis, so it is suitable for oil, encaustic (non-emulsified type), egg tempera and watercolor, but not fresco and casein.
Oil Absorption and Grinding
Prussian blue absorbs a moderately high amount of oil (45 grams of linseed oil per 100 grams of pigment) to make a paste.
Prussian blue is not considered toxic, however, care should be used in handling the dry powder pigment to avoid inhaling the dust.
Rublev Colours Pigment: Prussian Blue
|Color: ||Blue |
|Colour Index: ||Pigment Blue 27 (77510:1) |
|Chemical Name: ||Ammonium iron(III) hexacyanoferrate(II) |
|Chemical Formula: ||Fe(NH4) [Fe (CN)6]•xH2O |
|CAS Number: ||25869-00-5 |
|EINECS Number: ||247-304-1 |
|ASTM Lightfastness Rating |
|Acrylic: ||I |
|Oil: ||I |
|Watercolor: ||I |
|Lightfastness (1–8) |
|Full Shade ||7–8 |
|Tint ||2 |
|Chemical Resistance (1–5) |
|Acid ||4 |
|Alkali ||2 |
|Specific Gravity (g/cm3): ||1.80 |
|Refractive Index: ||1.56–1.662 |
|Particle Size (Average): ||400µm |
|pH (10% Aqueous Slurry): || 3.0–5.0 |
|Heat Stability: ||177° C (350° F) |
|Oil Absorption (g oil/100g): ||40–50 g |
|Munsell Value: ||4.54PB 2.43/6.16 |